+ Overall the game should have more fun aspect to it, GTAIV was a little to serious for my taste.

Major thing Rockstar needs to work on for the next GTA is combining the realism and fun. They've got realistic physics and graphics now, so just throw in some miniguns, jetpacks, and clowncars and you're set.

The way I see it, leaving the possibility open to do unrealistic things is more realistic than not allowing it at all.